[sclug] Mirror disks across machines like distributed RAID?

[Dickon Hood]

On Tue, Jan 05, 2010 at 18:42:35 +0000, Keith Edmunds wrote:
: On Tue, 5 Jan 2010 17:04:01 +0000, dickon-ml at fluff.org said:
: > I have had at work, and my conclusion is this: in all cases I've ever
: > seen, don't bother. Do it at the application layer instead: you'll save
: > yourself a hell of a headache, and a bundle of cash.

: You seem to be very against DRBD but without stating any real reason.

I don't mean to be: as I said, I have no experience of it.  I'm just not a
fan of HA disc; IME it's better to engineer your application so you don't
need it.

: In the case, for example, of an HA web server, putting the websites on a
: DRBD device seems straightforward and reliable. How would you propose
: doing that in the application layer (and saving the aforesaid bundle)?

HA webservers can usually be managed happily with the usual tricks:
clusters of machines, load balancers (if you insist), HSRP-alike failover,
virtual IP addresses and whatnot.  Or you can simply do what the BBC has
done for many years, and have a five-minute TTL on the DNS and ifconfig an
alias on another machine should one of the farm go down.  This sort of
thing isn't rocket science.

-- 
Dickon Hood

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